Total hip arthroplasty, or total hip replacement, is an orthopedic procedure in which a surgically implanted device replaces a worn, damaged, or diseased hip joint. The surgically implanted device assumes the functions of the replaced hip joint, including support and joint articulation. The components of the surgically implanted device typically include an acetabular cup, a femoral head, and a femoral stem. The acetabular cup is a socket implanted into the hip that receives the femoral head having a smooth hemispherical surface adapted for articulation with the acetabular cup. The opposite end of the femoral head is attached to a fitting on the femoral stem, which is attached at its other end to the femur of a patient.
The implanted device should be biocompatible, structurally strong, tough, and wear-resistant. Further, the articulation between the acetabular cup and the femoral head should produce relatively low frictional engagement. These requirements, often conflicting, affect the choice of materials used to construct implanted devices. In particular, the femoral head should possess a hard and wear-resistant articulating outer surface, while also possessing tough, crack-resistant material properties in the region where the femoral head attaches to the femoral stem.
Therefore, a need exists in the art for an articulating structure to be used in an implanted orthopedic device that simultaneously possesses high hardness at the joint articulating surface, and high toughness where the structure joins to the underlying attachment structures.